Active Matrix Organic Light Emitting Diode (abbreviated as AMOLED) panel has advantages like low power consumption, low production cost, wide viewing angle and fast response speed, whereby the AMOLED display has gradually replaced the traditional liquid crystal display. Organic light emitting diodes (OLEDs) are current-driven, with the working principle that the recombination of electrons and holes produces radiation light, that is, electrical energy is directly converted into light energy, whereby a stable current is required to control light emission in display.
Currently an OLED is driven by a Drive Thin Film Transistor (abbreviated as DTFT), and the DTFT is usually a P-type switch transistor. The DTFT has a gate electrode connected to a data input terminal Vdata, a source electrode connected to a constant voltage power supply input terminal VDD, and a drain electrode connected to the OLED. A voltage difference VGS is generated between VDD of the source electrode and Vdata of the gate electrode so that the DTFT is turned on to drive the OLED, and the driving current of the OLED IOLED=K(VGS−Vth)2, wherein Vth is the threshold voltage of the DTFT itself and K is constant.
As can be seen from the driving current formula abovementioned, the threshold voltage Vth of the DTFT will affect the driving current flowing through the OLED, while errors caused by manufacturing processes, device aging and other reasons will cause the threshold voltage Vth of the DTFT in each pixel unit to drift, cause deviation in the driving current flowing through the OLED, and further affect the display effect.